Fabrication of electronic circuit elements using liquid deposition techniques is of profound interest as such techniques provide potentially low-cost alternatives to conventional mainstream amorphous silicon technologies for electronic applications such as thin film transistors (TFTs), light-emitting diodes (LEDs), large-area flexible displays and signages, radio frequency identification (RFID) tags, photovoltaics, sensors, and the like. However, the deposition and/or patterning of functional electrodes, pixel pads, and conductive traces, lines and tracks which meet the conductivity, processing, and cost requirements for practical applications have been a great challenge.
Solution-processable conductors are of great interest for use in such electronic applications. Metal nanoparticle-based inks represent a promising class of materials for printed electronics. Some metal nanoparticles such as silver-containing nanoparticles may suffer from instability issue when stored in ambient atmosphere. There is an urgent need addressed by embodiments of the present invention to process such metal nanoparticle into highly conductive features.
Moreover, in order to stabilize metal nanoparticles, large or bulky stabilizers are often used, which usually results in high processing temperature and long processing time. These are not compatible with plastic substrate such as polyethylene terephthalate (PET) and fast manufacturing process. Therefore, there is a need addressed by embodiments of the present invention to develop a process that decreases processing temperature and/or shortens processing time.
The conventional method (“Conventional Method”), disclosed for example in U.S. Pat. Nos. 7,443,027 and 7,270,694, to form a highly electrically conductive feature comprising coalesced silver-containing nanoparticles for electronic circuit elements involves: forming a feature comprising uncoalesced silver-containing nanoparticles on a suitable substrate and heating the uncoalesced silver-containing nanoparticles to form coalesced silver-containing nanoparticles (wherein there is absent from the Conventional Method the use of the plasma treatment and acid-containing composition treatment described herein for embodiments of the present invention). This Conventional Method may not be able to achieve high electrical conductivity for aged silver-containing nanoparticles. Moreover, the Conventional Method may not be able to achieve high electrical conductivity at a lower temperature and shorter processing time for some applications such as a high speed manufacturing flexible device on PET substrate. In embodiments, the present invention addresses shortcomings of the Conventional Method.
The following documents provide background information:
Yiliang Wu et al., U.S. Pat. No. 7,443,027.
Yuning Li et al., U.S. Pat. No. 7,270,694.
El Sayed Megahed, U.S. Pat. No. 4,048,405.
T. M. Hammad et al., “The Effect of Different Plasma Treatments on the Sheet Resistance of Sol-gel ITO and ATO Thin Films,” Chinese Journal of Physics, Vol. 40, No. 5, pp. 532-536 (Oct. 2002).